One method of administering medicines is by subcutaneously implanting a medicinal pellet. In the past, this form of administration of drugs was not widely used. Recently, however, materials have been developed which allow a drug to be subcutaneously introduced or administered beneath the skin of a patient so that the drug is slowly released over a long period of time. Such implants allow a drug to be dispensed in a relatively uniform dose over many months or years. This method of administering drugs is becoming especially important and popular as a method of administering contraceptive implants.
While subcutaneous implantation may be done surgically using a scalpel to make the incision and a trocar and cannula to place the implant, such methods require a physician or other highly trained person. Recently, improved instruments for implanting subcutaneous medicaments have been developed. These instruments have several advantages over surgical implantation. The instruments typically require far less skill to operate, and thus may be used by a paramedic or nurse. The instruments generally require less time to perform an implantation procedure.
Additionally, these instruments are frequently less intimidating and therefore more psychologically acceptable to a patient than are surgical procedures. This last advantage can be of great importance in some applications. For example, implantation of long term contraceptive devices is extremely attractive in many underdeveloped countries having an over-population problem. Typically, the potential subjects for administration of long term contraceptive implants in these countries are located in areas remote from modern medical care. The patients who could most benefit from such contraceptive methods are frequently unfamiliar with modern medicine and its techniques and instruments.
In such patients, the "intimidation factor" of an implantation procedure may be a major factor in whether or not a potential patient decides to accept the procedure. For these reasons, it is important that a device for performing subcutaneous implantation should be able to perform the desired implantation with minimal psychological and physical trauma to a patient.
The materials in which contraceptive steroids are imbedded in subcutaneous implantation are normally biologically inert polymers, some of which are biodegradable. The pellets made from such materials are typically long and cylindrical in cross section, and the size of these materials is on the order of the size of a pencil lead. The materials are generally flexible ranging from somewhat flexible to very flexible nature. See, for example, U.S. Pat. No. 4,451,253 which describes some exemplary contraceptive pellets and an apparatus for individually implanting such pellets subcutaneously.
The size and shape of an implant pellet are important in determining the rate of delivery of a particular drug from a subcutaneous implant. Practical considerations put constraints on the dimensions which a subcutaneous implant may have. In particular, the length of an implant is generally limited. A typical implant is on the order of 1 1/2 to 2 inches long. Longer implants are much more difficult to accurately locate. They are also more susceptible to breakage, which may affect the drug delivery rate and, in general, they are simply more cumbersome and cosmetically apparent. Because of this, it is frequently necessary to implant a desired amount of a drug as a plurality of individual, shorter implant pellets rather than as a single longer pellet. Thus, an instrument which can quickly allow a physician or nurse to implant a plurality of pellets with minimal physical and psychological trauma to a patient would be desirable. When implanting several implants, care must be taken to accurately place the implants in a manner such that one does not interfere with the dissolution of the others.